1. Field of the Invention
The present invention relates to an ink jet recording head applied to an ink jet printer particularly a bubble jet printer utilizing an bubbling phenomenon, and an ink jet recording apparatus having such an ink jet recording head.
2. Related Background Art
A recording head applied to a bubble jet recording system generally includes minute discharge ports, flow paths, and heat generating members provided in the flow paths.
The bubble jet recording system means a recording system in which a bubble is generated in liquid due to film-building caused locally increasing the liquid in the flow path by utilizing the heat generating member and the liquid is discharged from the minute discharge port by utilizing high pressure of the bubble, thereby adhering the liquid onto a recording paper and the like.
In order to obtain high quality of an image recorded by such a recording technique, a minute liquid droplets must be discharged with high density. To this end, it is fundamentally important to form minute flow paths and minute heat generating sources. Thus, in the bubble jet recording system, by making use of simplicity of the structure, there has been proposed a method for manufacturing a high density head by utilizing a photolithography technique (For example, refer to Japanese Patent Application Laid-Open No. 08-15629). Further, in order to adjust a discharge amount of liquid droplets, a heat generating member including a central portion having a heat generating amount greater than those in end portions (Refer to Japanese Patent Application Laid-Open No. 62-201254). As the heat generating member, generally, a thin film resistance body made of tantalum nitride is used, and the liquid is bubbled by Joule heat generated by energizing the heat generating member. In such a heat generating member, in order to prevent damage of a surface of the heat generating resistance body due to cavitation, generally, an anti-cavitation layer having a thickness of about 0.2 xcexcm and made of metal such as Ta is provided on the surface via an insulator having a thickness of about 0.8 xcexcm and made of SiN.
Further, Japanese Patent Application Laid-Open No. 64-20150 discloses a multi nozzle ink jet head characterized in that a plurality of vertical and lateral wirings are provided on a substrate, and rectifying elements permitting flow of only normal electric current and heat generating elements connected to the rectifying elements are provided at junctions between the vertical wirings and the lateral wirings. Further, Japanese Patent Application Laid-Open No. 57-36679 discloses a thermal head in which diodes capable of generating heat by energization in normal direction are arranged as plural arrays.
In conventional multi nozzle heads, when the heat generating elements connected to the junctions between the vertical wirings and the lateral wirings are selectively driven in a matrix fashion, noise voltage smaller than drive voltage may be added to non-selected heat generating elements to generate undesirable heat. The Inventors found that the heat generating element may have directly or indirectly a current/voltage property indicating a low resistance value at a high voltage side and a high resistance value at a low voltage side in order to prevent generation of heat if the noise voltage is applied to the non-selected heat generating element. As elements having such a current/voltage property, there are a MIM element and a barister.
Further, in many conventional heads, it is assumed that the heat generating elements diodes and logic circuits are simultaneously formed on a silicon substrate by a semiconductor process (such as ion injecting method). Accordingly, a head having relatively few nozzles can be made relatively compact and cam be formed by a single process. However, for example, in a full multi head having a length corresponding to entire width of a recording paper, if the head is manufactured as a single piece, a length of 12 inches is required, and, thus, it is difficult to use a normal silicon wafer, which may make a manufacturing method expensive.
If ink jet heat generating elements having non-linear elements such as MIM elements which can be manufactured without using a conventional semiconductor process such as the ion injecting method can be driven in the matrix fashion, there is the possibility that an elongated ink jet head can be provided at a low cost.
However, since MIM element has a non-linear property in the current/voltage property that the current value is changed sensitively depending upon the voltage value, if drive voltage of a power source is changed slightly, the current flowing through the MIM element is changed greatly, with the result that the heat generating element (heater) as a bubble generating portion may be heated excessively to damage the heater or poor discharging may occur due to insufficient heating. Thus, adjustment of the drive voltage of the power source becomes very severe.
An object of the present invention is to provide an ink jet recording head which utilizes an MIM element capable of realizing an elongated ink jet head with a low cost and which can prevent excessive heating and poor heating of a BJ heater by suppressing great fluctuation of an electric power supplying amount of the MIM element due to minute change in the drive voltage of a power source, and an ink jet recording apparatus having such an ink jet recording head.
To achieve the above object, according to a first aspect of the present invention, there is provided an ink jet recording head comprising heat generating means for generating thermal energy utilized to discharge ink, a non-linear element having a non-linear current/voltage property and adapted to drive the heat generating means, and current adjusting means for adjusting current flowing into the non-linear element.
In this case, the current adjusting means may be a current adjusting resistor connected to the non-linear element in series. The current adjusting resistor is preferably constituted by a heat generating resistance body, a wiring resistor or an adjusting resistor. Further, a resistance value of the current adjusting resistor is from 0.1 to 10 times, preferably, about 1 time or 2 times, of a resistance value of the non-linear element in an operating condition. The non-linear element used in such a recording head is preferably a non-linear element indicating MIM type electrical characteristics.
In the above-mentioned ink jet recording head, the heat generating means may also act as the non-linear element or the heat generating means may be formed independently from the non-linear element.
Further, according to a second aspect of the present invention, there is provided an ink jet recording head comprising heat generating means including a heat generating resistance member for generating thermal energy utilized to discharge ink and a pair of electrodes connected to the heat generating resistance member, and a non-linear element connected to the heat generating resistance member in series, and wherein the heat generating resistance member is used as a current adjusting resistor for adjusting electrical current flowing in a circuit in which the non-linear element is connected to the heat generating resistance member in series.
In this case, a resistance value of the heat generating resistance member is from 0.1 to 10 times, preferably, about 1 time or about 2 times, of a resistance value of the non-linear element in an operating condition. Particularly when the non-linear element is a non-linear element indicating the MIM type electrical characteristics, an ink jet recording head wherein a two-terminal circuit unit in which the non-linear element is connected to the heat generating resistance member in series is disposed at a junction of a matrix circuit and wiring resistance of the two-terminal circuit unit is substantially zero and the resistance value of the heat generating resistance member is about 1 time of the resistance value of the non-linear element and matrix driving of xc2xd bias system is effected on the matrix circuit, or an ink jet recording head wherein a two-terminal circuit unit in which the non-linear element is connected to the heat generating resistance member in series is disposed at a junction of a matrix circuit and wiring resistance of the two-terminal circuit unit is substantially zero and the resistance value of the heat generating resistance member is about 2 times of the resistance value of the non-linear element and matrix driving of ⅓ bias system is effected on the matrix circuit is preferable.
Further, according to a third aspect of the present invention, there is provided an ink jet recording head comprising heat generating means for generating thermal energy utilized to discharge ink, a non-linear element for driving the heat generating means, and a wiring for energizing the non-linear element, and wherein resistance of the wiring is used as a current adjusting resistor for adjusting current flowing in a circuit including the non-linear element and the wiring.
In this case, a resistance value of the wiring resistor is from 0.1 to 10 times, preferably, about 1 times or about 2 times, of a resistance value of the non-linear element in an operating condition, and the non-linear element is preferably a non-linear element indicating the MIM type electrical characteristics.
Further, according to a fourth aspect of the present invention, there is provided an ink jet recording head comprising heat generating means for generating thermal energy utilized to discharge ink, a non-linear element having a non-linear current/voltage property and adapted to drive the heat generating means, and matrix electrodes constituting a matrix circuit for applying voltage to the heat generating means, and wherein the non-linear element is disposed at a junction of the matrix circuit and the current/voltage property at the junction has differential resistance of 40 to 250 xcexa9 at drive voltage of the heat generating means. In this case, the heat generating means is a heat generating resistance member, and a two-terminal circuit unit in which the non-linear element is connected to the heat generating resistance member in series is disposed at the junction of the matrix circuit.
Further, according to a fifth aspect of the present invention, there is provided an ink jet recording head comprising heat generating means for generating thermal energy utilized to discharge ink, a non-linear element having a non-linear current/voltage property and adapted to drive the heat generating means, and matrix electrodes constituting a matrix circuit for applying voltage to the heat generating means, and wherein the non-linear element is disposed at a junction of the matrix circuit and the current/voltage property at the junction is such that effective current starts to flow the junction from voltage of about xc2xd time of operating voltage and desired current flows at the operating voltage. In this case, the heat generating means is a heat generating resistance member, and a two-terminal circuit unit in which the non-linear element is connected to the heat generating resistance member in series is disposed at the junction of the matrix circuit.
Further, according to a sixth aspect of the present invention, there is provided an ink jet recording head comprising heat generating means for generating thermal energy utilized to discharge ink, a non-linear element having a non-linear current/voltage property and adapted to drive the heat generating means, and matrix electrodes constituting a matrix circuit for applying voltage to the heat generating means, and wherein the non-linear element is disposed at a junction of the matrix circuit and the current/voltage property at the junction is such that effective current starts to flow the junction from voltage of about ⅓ time of operating voltage and desired current flows at the operating voltage. In this case, the heat generating means is a heat generating resistance member, and a two-terminal circuit unit in which the non-linear element is connected to the heat generating resistance member in series is disposed at the junction of the matrix circuit.
Further, in the recording head according to the present invention, preferably, there is provided matrix electrodes constituting a matrix circuit for applying voltage to the heat generating means, and, in this case, the non-linear element is preferably disposed at a junction of the matrix circuit. In the recording heads according to the first to third aspects, preferably, the ink is discharged by causing film-boiling in the ink by the thermal energy.
Further, an ink jet recording apparatus according to the present invention is characterized by an ink jet recording head according to the above first, second or third aspect in which an ink discharge port is disposed a confronting relationship to a recording surface of a recording medium, and conveying means for conveying the recording medium.
Further, an ink jet recording apparatus according to the present invention is characterized in that it comprises an ink jet recording head comprising heat generating means including a heat generating resistance member for generating thermal energy utilized to discharge ink and a pair of electrodes connected to the heat generating resistance member, and a non-linear element connected to the heat generating resistance member in series and indicating MIM type electrical characteristics and in which the heat generating resistance member is used as a current adjusting resistor for adjusting current flowing in a circuit in which the non-linear element is connected to the heat generating resistance member in series, and conveying means for conveying a recording medium, and wherein a resistance value of the heat generating member is from 0.1 to 10 times, preferably, about 1 time or about 2 times, of a resistance value of the non-linear element in an operating condition.
In this case, an ink jet recording apparatus in which a two-terminal circuit unit in which the non-linear element is connected to the heat generating resistance member in series is disposed at a junction of a matrix circuit and wiring resistance of the two-terminal circuit unit is substantially zero and the resistance value of the heat generating resistance member is about 1 time of the resistance value of the non-linear element and matrix driving of xc2xd bias system is effected on the matrix circuit, or an ink jet recording apparatus in which a two-terminal circuit unit in which the non-linear element is connected to the heat generating resistance member in series is disposed at a junction of a matrix circuit and wiring resistance of the two-terminal circuit unit is substantially zero and the resistance value of the heat generating resistance member is about 2 times of the resistance value of the non-linear element and matrix driving of ⅓ bias system is effected on the matrix circuit is preferable.
With the arrangement as mentioned above, by providing the non-linear element (particularly, non-linear element having the MIM type electrical characteristics) and the current adjusting means for adjusting the current flowing in the non-linear element in series, particularly, heat generating resistance member or wiring resistor) in a heat driving circuit for effecting ink jet discharging, change in current flowing in the circuit is suppressed, thereby suppressing great change in an electrical power supplying amount of the MIM element due to minute change in voltage of the discharge driving power source. Thus, excessive heating or poor heating of the ink jet heater can be prevented. Further, since the ink jet heater can be effectively driven in the matrix fashion by using the non-linear element which can be manufactured without using the conventional semiconductor process such as an ion injecting method, an inexpensive elongated ink jet head can be provided.